[PD] PD, arduino and sharp range detectors

[Tim Boykett]

that seems to be the case!

thanks

tim


On 30 Oct 2008, at 17:41, Martin Peach wrote:

> Tim Boykett wrote:
>>   We are having trouble with a PD - Arduino - Sharp IR gp2d12 IR
>> range sensor.
>>
>> everything works for a while, then the arduino just stops and  
>> sometimes
>> takes PD down with it. once we had a warning from the OS that there
>> was too much current
>> being sucked on the USB port.
>>
>> we are using three such things, each uses typically 33 and up to 50
>> mA. This
>> should (according to the Arduino and USB specs) not be too much, but
>> perhaps
>> these are wrong.
>
> I have built a circuit with six of those sensors on an Arduino  
> Diecimila, it
> worked fine with external power, but I didn't even try it with USB  
> power
> because for me 50mA is too much. (At first it crashed sporadically  
> because I
> was sending too much data through the serial port.) The actual USB  
> port you
> are using may not be able to supply that much current even if the USB
> circuit is able to handle it. If it only happens occasionally it's  
> probably
> because the sensors sometimes pull more than the average current, so a
> ~100uF capacitor on the power pins would help, but you should really  
> use a
> separate power supply for the sensors, or just power the entire  
> Arduino
> externally.
>
> Martin
>
>
>
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